Motion-sensitive cameras stationed in the northern part of the park captured two images—possibly of the same animal—one in December and one in January.

The little-seen fox was sighted north of the park in 2010, but no one's seen it inside the park's boundaries since 1916. To say researchers are excited would be an understatement. (Related: "'Lost' Fox Subspecies Found via Saliva Analysis.")

"Knowing that the animal is in the park is huge for us," said park wildlife biologist Sarah Stock. "Up until this point we had observations, but none of them were substantiated."

Why It Matters

The Sierra Nevada red fox (Vulpes vulpes necator) is incredibly rare, with as few as 50 individuals thought to exist in North America. Prized for their vibrant coats, red fox populations were devastated by hunting and trapping during the 19th and 20th centuries. (See stunning photos of ten extremely rare animals.)

The fox, which historically ranged throughout the Sierra Nevada mountains, is now limited to two small populations in California: one around Lassen Volcanic National Park and another around Sonora Pass.

"Now we know [that population] extends down to northern Yosemite," said Stock.

She added that other human threats, such as livestock grazing, snowmobiling, and logging, could affect the fox's survival.

"Trapping was banned in 1974, so we actually have a pretty long history of impacting this animal," she said.

The Big Picture

It's too soon to say whether the Sierra's population is rebounding or expanding its range, as researchers are just now getting to know the elusive Sierra Nevada red. (Take an endangered species quiz.)

"At this point we're still gathering the most basic information, still just establishing baselines," Stock said.

The find is meaningful because a Sierra Nevada red fox population within Yosemite's borders would enjoy the special protections of a national park, where harmful activities such as logging and livestock raising are off-limits.

The fox, which is protected by the state of California, is being considered for listing under the Endangered Species Act.

What's Next

Stock says the next step is to continue detecting foxes using cameras and so-called "hair snares"—bristle brushes that collect hair samples when a fox walks by.